Cron Expression Parser

• This is a Java-based project for parsing and working with cron expressions.
• Cron expressions are commonly used to schedule tasks or events to run at specific times and intervals.

Features

• Expand cron expressions into lists of valid values.
• Supports the standard cron expression format with five fields: minute, hour, day of month, month, and day of week.
• Followed, at the end by a command.
• Not handling the special time strings such as "@yearly".
• Tokens are separated by SPACE character.
• Example
  • */15 0 1,15 * 1-5 ls

Fields	Allowed Special Characters
Minute	*,/-
Hour	*,/-
Day of Month	*,/-?
Month	*,/-
Day Of Week	*,/-?

Getting Started

Prerequisites

• Java 17 or higher.
• Gradle

Installation

Getting Codebase

• Download code from drive and unzip

Installing Java 17

• OS X

  brew install openjdk@17

• Linux

  sudo apt-get update
  sudo apt-get install openjdk-17-jdk

Installing gradle

• OS X

    brew install gradle

• Linux

  sudo apt-get update
  sudo apt-get install gradle

Building Jar

• Move to the project root & run following command
• OS X / Linux

  ./gradlew jar

• You can locate the generated JAR file in the "build/libs" directory. It will have a name like " your-project-name-version.jar".

Running Jar

Open in the directory where the jar file is present.

  java -jar {jarName}.jar "cron_expression"

  java -jar cronparser-1.0-SNAPSHOT.jar "*/15 0 1,15 * 1-5 /usr/bin/find"

Required Field : argument (cron_expression), else exception will be thrown.

Examples

1. Parsing correct cron expression

  java -jar cronparser-1.0-SNAPSHOT.jar "*/15 0 1,15 * 1-5 /usr/bin/find"

Output

2. Parsing incorrect expression with missing field.

   java -jar cronparser-1.0-SNAPSHOT.jar "**"

Output